The wrapper project

Joe Armstrong <>
Thu Aug 21 15:24:24 CEST 2003




On Thu, 21 Aug 2003, Joachim Durchholz wrote:

> Joe Armstrong wrote:
> > 2) The components must communicate by asynchronous message passing
> 
> I have an exception to consider:
> When composing subcomponents from components,

  Uugh - do you mean the other way around?

  You make components from sub-components ... ????

> *and* a crashing subcomponent shall crash the entire component,
> *then* synchronous communication is appropriate.

  I assume you meant that

   1) components are made from sub-components
   2) if a sub-component crashes you want the component to crash

  To do this (if that's what you meant) I would like asynchronous messages.

  The problem  with synchronous messages  is that you  can't implement
them.  The laws  of physics preclude this. You need  to send a message
between the  systems (which  even at the  speed of light  takes finite
time) to  send information between the  systems - you  also change the
state.
 

> At least if that "synchronous communication" is a simple subroutine call 
> - emulating synchronous messages on top of an asynchronous layer like 
> Erlang's messages and pipes isn't doing much good.
> 

  But I wouldn't  emulate synchronous messages on top  of the messages
and pipes I'd use discrete events or RPC's with timeouts. I would also
make no assumptions about the cause of the absence of a message.

/Joe




> Just my 2c.
> Flame me as appropriate :-)
> 
> Regards,
> Jo
> 




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